The present invention relates generally to a hole-saw device for cutting holes in wood material; more particularly, the invention relates to a hole saw having chipper teeth for facilitating the cutting operation.
Hole-cutting saw devices are well known in the art, the most typical prior art device being one which merely constrains a saw-toothed blade in a circular loop. The tooth pattern of such devices usually adapts conventional saw-toothed techniques to provide a series of sharpened metal points aligned around a circular path wherein each toothed point may be aligned slightly outwardly or inwardly from the vertical in order to widen the cutting pattern. A widened cutting pattern offers the advantage of cutting a circular groove which is wider than the thickness of the cutting blade, and therefore it eases the frictional forces of the wood against the side surfaces of the blade. The cutting effectiveness of such a device depends upon the force applied against the cutting tool so that the sharpened saw blade points are forced to bite into the wood material and thereby to remove particles of material. If no axial force is applied against the cutting tool, devices of this type will generally merely turn in the saw groove without removing material from the bottom of the saw groove.
The foregoing operation of conventional hole-cutting saws is to be contrasted with the operation of other cutting tools, such as chain saws. The chain saw cutting tool utilizes a series of aligned links which are propelled in an endless loop via a chain drive mechanism but always along a linear cutting path. Each link comprises a small wood chipper wherein the link has a forward gauge plate to restrain the depth of chipping and cutting, followed by a rearward curved and sharpened blade edge which is positioned at an elevation higher than the gauge member. The elevation distance between the sharpened blade edge and the gauge member determines and limits the depth of chipping; i.e., the chipper blade's natural propensity to bite deeply into the wood surface is limited by the gauge which rides along the bottom of the groove just ahead of the chipper cutting edge. Chain saws utilize this principle to rapidly and efficiently cut through wood materials, principally trees; and if each of the chipper teeth are well sharpened, there is no external force required to facilitate the cutting operation. The weight of the chain saw blade and guide bar by itself, together with the natural propensity of the chipper to dig into the wood material, enables the chain saw to guide itself through a cut in a wood material.
Because a certain axial force is required to drive a hole cutting saw through wooden materials, it becomes increasingly difficult to cut holes of increasing diameter. In the construction trades, particularly the plumbing and heating/ventilating trade, it frequently becomes necessary to cut enlarged holes for the passage of pipes and heating ducts. Such hole saws as required for these operations may be required to cut up to six-inch diameter holes; the axial force and torque required against the cutting tool for a six-inch diameter hole is quite large and may be beyond the capabilities of some workmen and power drills. It, therefore, would be a significant advantage to provide a hole-cutting device which operates with substantially lowered axial force in order to complete a cutting operation.